JPH06279927A - High strength rail excellent in ductility and toughness and its production - Google Patents
High strength rail excellent in ductility and toughness and its productionInfo
- Publication number
- JPH06279927A JPH06279927A JP7019493A JP7019493A JPH06279927A JP H06279927 A JPH06279927 A JP H06279927A JP 7019493 A JP7019493 A JP 7019493A JP 7019493 A JP7019493 A JP 7019493A JP H06279927 A JPH06279927 A JP H06279927A
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- mns
- toughness
- rail
- pearlite
- steel
- Prior art date
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、レール鋼のパーライト
組織を微細化して延性および靭性の向上を図った高強度
レールの製造法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength rail in which the pearlite structure of rail steel is refined to improve ductility and toughness.
【０００２】[0002]
【従来の技術】近年、鉄道輸送は高荷重化、高速化が指
向され、レールに要求される特性がますます厳しくなっ
ている。高荷重鉄道では急曲線区間の摩耗対策、レール
頭部内部疲労損傷対策が要求され、高速鉄道では主とし
て直線区間の表面損傷が課題として挙げられている。こ
れらに加えて、寒冷地においては、冬季にレール破断が
集中的に発生する傾向が認められており、寒冷地鉄道で
のレール材の靭性改善は、安全な鉄道輸送に欠かせない
特性になっている。2. Description of the Related Art In recent years, railway transportation has been aimed at higher loads and higher speeds, and the characteristics required for rails have become increasingly severe. For heavy-duty railways, measures against wear on sharp curves and internal fatigue damage to rail heads are required. On high-speed railways, surface damage mainly on straight sections is cited as an issue. In addition to these, it is recognized that rail rupture tends to occur intensively in winter in cold regions, and improving the toughness of rail materials in cold region railways is a characteristic that is essential for safe rail transportation. ing.
【０００３】また、鉄道輸送の高効率化のために、高速
化および貨物の重積載化が進められているが、これに伴
ってレール頭部の摩耗や疲労損傷が急速に増加しつつあ
る。このようなレール材の使用環境の過酷化、特に摩耗
の増加に対処するために、レール鋼の高強度化のための
技術開発が加速され、国内・外を問わず曲線区間のレー
ル材はほとんどすべて高強度レールが支配することとな
った。Further, in order to improve the efficiency of rail transportation, speeding up and heavy loading of cargo have been promoted, but along with this, wear and fatigue damage of rail heads are rapidly increasing. In order to cope with such harsh environment of use of rail materials, especially increase in wear, technological development for strengthening rail steel has been accelerated, and rail materials in curved sections are mostly used in Japan and abroad. All of the high-strength rails now dominate.
【０００４】しかし、一方ではレール鋼の耐摩耗性の向
上とともに、本来摩耗によって削り取られるべき疲労ダ
メージ層がレール頭表面、特に車輪フランジ付け根部が
押し付けられるゲージ・コーナー（ＧＣ）表面に残存
し、表面損傷を生成させる傾向が認められるようになっ
た。さらにレール鋼の耐摩耗性の向上は、車輪荷重のレ
ールＧＣ内部での応力集中を一点に固定させることとな
り、レール頭部内部からの疲労損傷を急増させることと
なった。このようなレール頭表面損傷性の改善および内
部疲労損傷に対する抵抗性を改善するためには、レール
材質として靭性および延性を向上させることが重要であ
る。On the other hand, on the other hand, as the wear resistance of the rail steel is improved, a fatigue damage layer that should be scraped off due to wear remains on the rail head surface, especially on the gauge corner (GC) surface where the wheel flange root is pressed, A tendency to produce surface damage has become apparent. Further, the improvement of the wear resistance of the rail steel means that the stress concentration inside the rail GC due to the wheel load is fixed at one point, and the fatigue damage from the inside of the rail head rapidly increases. In order to improve such rail head surface damage and resistance to internal fatigue damage, it is important to improve the toughness and ductility of the rail material.
【０００５】高強度レールの靭性および延性改善の方策
としては以下の方法が考えられる。 （１）普通圧延後一旦室温まで冷却したレール頭部を低
温度で再加熱した後加速冷却する方法。 （２）制御圧延によりオーステナイト粒を微細化した後
レール頭部を加速冷却する方法。 （３）制御圧延した後、パーライト変態前で低温度に再
加熱し、その後加速冷却する方法。The following methods are considered as measures for improving the toughness and ductility of the high-strength rail. (1) A method in which a rail head that has been once cooled to room temperature after normal rolling is reheated at a low temperature and then accelerated cooling is performed. (2) A method of accelerating and cooling the rail head after refining austenite grains by controlled rolling. (3) A method in which after controlled rolling, it is reheated to a low temperature before pearlite transformation and then accelerated cooling is performed.
【０００６】[0006]
【発明が解決しようとする課題】上記方法の（１）で
は、大幅な靭性・延性改善のためには特開昭５５−１２
５２３１号公報に記載されているような通常の加熱温度
よりも低い８５０℃以下の低温度に再加熱し、オーステ
ナイト粒度を微細にすることによって靭性および延性を
改善しようとするもので、低温度で加熱してかつレール
頭部内部まで加熱を深めようとすると、投入熱量を下げ
て長時間加熱する必要がある。このため熱処理生産性を
著しく阻害し製造コストを高める難点がある。また
（２）の方法は特開昭５２−１３８４２７号公報および
特開昭５２−１３８４２８号公報に記載されているよう
に、圧延時のオーステナイト粒の細粒化によって靭性・
延性の向上を図ろうとすると、高温での大圧下が要求さ
れ、レール圧延機の能力あるいはレールの形状制御の観
点からも問題を含んでいる。さらに（３）の方法は、特
公平４−４３７１号公報に記載されているように、８０
０℃以下で５％以上の圧延を実施した後、再度７５０〜
９００℃に加熱することによりオーステナイト粒を微細
にしようとする方法であり、圧延後に低温再加熱のため
の加熱炉を必要とするため作業性、生産性、製造コスト
の観点から問題が多い。In the above method (1), in order to improve the toughness and ductility to a great extent, JP-A-55-12 is used.
Reheating to a low temperature of 850 ° C. or lower, which is lower than the normal heating temperature as described in Japanese Patent No. 5231, attempts to improve toughness and ductility by making the austenite grain size fine. When heating and deepening the heating to the inside of the rail head, it is necessary to lower the amount of heat input and heat for a long time. Therefore, there is a problem that heat treatment productivity is significantly impaired and manufacturing cost is increased. Further, the method (2), as described in JP-A-52-138427 and JP-A-52-138428, provides toughness by fine austenite grains during rolling.
In order to improve the ductility, a large reduction at high temperature is required, which causes a problem from the viewpoint of rail rolling mill capacity or rail shape control. Furthermore, the method (3) is described in Japanese Patent Publication No.
After rolling 5% or more at 0 ° C. or less, 750 to 750 again
This is a method in which the austenite grains are made fine by heating at 900 ° C. Since a heating furnace for low-temperature reheating after rolling is required, there are many problems from the viewpoint of workability, productivity, and manufacturing cost.
【０００７】本発明はこのような従来の問題点を解消す
るものであって、オーステナイト粒内より微細なパーラ
イトを生成させることにより、微細パーライト組織を有
する延性および靭性に優れた高強度レールおよびその製
造法を提供することを目的とする。The present invention solves the above-mentioned problems of the prior art, and by producing finer pearlite than in austenite grains, a high-strength rail having a fine pearlite structure and excellent in ductility and toughness, and the same. The purpose is to provide a manufacturing method.
【０００８】[0008]
【課題を解決するための手段】本発明は脱酸元素として
Ｔｉを添加して脱酸処理を施して溶製した。すなわち、
重量％で、Ｃ ：０．５５〜０．８５％、 Ｓｉ：０．
２０〜１．２０％、Ｍｎ：０．５０〜１．５０％、 Ｓ
：０．００２〜０．０３５％、Ｃｒ：０．１〜１．０
％、 Ｖ ：０．０１〜１．０％を含有し、残部が
鉄および不可避的不純物からなるレール鋼でかつ０．１
〜１０μｍの大きさのＭｎＳ個数がレール鋼中の１mm2
あたり、３０〜１００００個存在することを特徴とする
延性および靭性に優れた高強度レールである。また本発
明では、従来オーステナイト粒界のみからしか生成しな
いといわれていたパーライト変態を、オーステナイト粒
内のＭｎＳにパーライト変態の核となるＶ炭化物（Ｖ
Ｃ）を配して、オーステナイト粒内からもパーライト変
態を生成させることを特徴としており、粒界から変態す
るパーライトに加えて、オーステナイト粒内のＭｎＳの
生成核を制御・促進させることにより、粒内から生成し
たパーライトによって著しく組織が微細化し、これに伴
って大幅な靭性および延性の改善を図ることができる。According to the present invention, Ti was added as a deoxidizing element and a deoxidizing treatment was performed to melt the alloy. That is,
% By weight, C: 0.55 to 0.85%, Si: 0.
20 to 1.20%, Mn: 0.50 to 1.50%, S
: 0.002-0.035%, Cr: 0.1-1.0
%, V: 0.01 to 1.0%, the balance being rail steel consisting of iron and unavoidable impurities, and 0.1
The number of MnS with a size of 10 μm is 1 mm 2 in the rail steel.
Therefore, it is a high-strength rail excellent in ductility and toughness, characterized by the presence of 30 to 10,000 pieces. Further, in the present invention, the pearlite transformation, which has been conventionally said to be generated only from austenite grain boundaries, is converted into MnS in the austenite grains by the V carbide (V
C) is arranged to generate a pearlite transformation also from within the austenite grains. In addition to pearlite transformed from the grain boundaries, MnS formation nuclei in the austenite grains are controlled / promoted to form grains. The structure is remarkably refined by the pearlite generated from the inside, and along with this, the toughness and ductility can be greatly improved.
【０００９】さらに本発明は、前記組成からなるレール
鋼を溶鋼を造塊・分塊法あるいは連続鋳造法を経て製造
した鋼片を、通常圧延後あるいはレール頭部もしくは底
部も含めて通常温度に再加熱した後、冷却過程でオース
テナイト域温度から冷却する際に７００〜５００℃の間
を１〜５℃/secで加速冷却する方法を付与することによ
って、オーステナイト粒内のＭｎＳを核とするパーライ
トの変態温度を低下せしめ、ＭｎＳを核とするパーライ
トによる組織微細化を通じての靭性改善をより顕著にす
ることが可能である。すなわち図１に示すように、Ｖ添
加なしの場合の加速冷却による靭性改善の程度に比べ、
Ｖを添加し粒内パーライトを生成させた場合の加速冷却
による靭性改善の程度の方が大幅に大きい。また、加速
冷却による高強度化によって耐摩耗性にも優れた高強度
レールを製造することができる。Further, the present invention provides a steel slab produced by subjecting a rail steel having the above-mentioned composition to a molten steel through an ingot-casting method, an ingot-casting method, or a continuous casting method, to a normal temperature after normal rolling or including the rail head or bottom. After reheating, the pearlite having MnS in the austenite grain as a nucleus is provided by adding a method of accelerating cooling at 700 to 500 ° C. at 1 to 5 ° C./sec when cooling from the austenite region temperature in the cooling process. It is possible to lower the transformation temperature of and improve the toughness through the refinement of the structure by pearlite having MnS as the nucleus. That is, as shown in FIG. 1, compared with the degree of improvement in toughness due to accelerated cooling without V addition,
The degree of improvement in toughness due to accelerated cooling when V is added to generate intragranular pearlite is significantly greater. In addition, high strength rails having excellent wear resistance can be manufactured by increasing the strength by accelerated cooling.
【００１０】[0010]
【作用】以下に本発明について詳細に説明する。先ず、
脱酸の必要性および脱酸元素としてＴｉに限定した理由
について述べる。本発明における脱酸の目的はＭｎＳの
核となる酸化物の制御を目的としたものであり、Ｔｉは
ＭｎＳの生成核として有効な酸化物（Ｔｉ2 Ｏ3 ）の構
成元素として、ＭｎＳの個数と分布を制御する目的で添
加する。なお、一般的に脱酸剤として用いられているＡ
ｌは、レール内部からの疲労損傷の発生に有害なアルミ
ナクラスターを生成させることからその添加を行わな
い。The present invention will be described in detail below. First,
The necessity of deoxidation and the reason why it is limited to Ti as the deoxidizing element will be described. The purpose of deoxidation in the present invention is to control the oxide that serves as the core of MnS, and Ti is the number of MnS as the constituent element of the oxide (Ti 2 O 3 ) that is effective as the nucleus for forming MnS. And for the purpose of controlling the distribution. A, which is generally used as a deoxidizer,
Since l produces alumina clusters that are harmful to the occurrence of fatigue damage from inside the rail, its addition is not performed.
【００１１】上記脱酸後の０．１〜１０μｍのＭｎＳ個
数を１mm2 あたり３０〜１００００個に限定した理由を
述べる。十分な脱酸によって酸素が低減し、その結果微
細な酸化物が生成し、この酸化物を核としてＭｎＳがオ
ーステナイト中に微細分散し、さらにこのＭｎＳを核と
してＶ炭化物（ＶＣ）が生成する。このオーステナイト
粒内のＭｎＳを核としたＶ炭化物からパーライト変態が
生成するわけであるが、この際０．１μｍ以下の大きさ
のＭｎＳでは、Ｖ炭化物の核とはなりがたく、また１０
μｍ以上のＭｎＳを生成させると、ＭｎＳの絶対数が減
少してしまい、結果的にパーライトの核となるＭｎＳの
数が減少してしまうため、ＭｎＳの個数を０．１〜１０
μｍに限定した。また、ＭｎＳの個数を１mm2 あたり３
０〜１００００個に限定した理由は、３０個以下のＭｎ
Ｓでは靭性・延性を改善するための十分な核生成サイト
を確保できないからであり、また１００００個以上のＭ
ｎＳが生成するとレール鋼自体が汚染されてかえって靭
性・延性が低下することから、１mm2 あたりのＭｎＳ個
数を３０〜１００００個に限定した。The reason why the number of MnS of 0.1 to 10 μm after deoxidation is limited to 30 to 10,000 per 1 mm 2 will be described. Oxygen is reduced by sufficient deoxidation, and as a result, a fine oxide is generated, MnS is finely dispersed in austenite with this oxide as a nucleus, and V carbide (VC) is further generated with this MnS as a nucleus. The pearlite transformation is generated from the V carbide having MnS as the nucleus in the austenite grains. At this time, MnS having a size of 0.1 μm or less does not easily form the nucleus of the V carbide.
When MnS of μm or more is generated, the absolute number of MnS decreases, and as a result, the number of MnS, which is the nucleus of pearlite, decreases.
Limited to μm. Moreover, the number of MnS is 3 per 1 mm 2.
The reason for limiting the number to 0 to 10000 is that Mn of 30 or less
This is because S cannot secure a sufficient nucleation site for improving the toughness and ductility.
When nS is produced, the rail steel itself is contaminated and the toughness and ductility are rather deteriorated. Therefore, the number of MnS per 1 mm 2 is limited to 30 to 10,000.
【００１２】次に、上記脱酸を行った溶鋼の化学成分を
前記のように限定した理由について述べる。Ｃは高強度
化およびパーライト組織生成のための必須元素であり、
また耐摩耗性に対しても一義的に効果を示す元素である
が０．５５％未満ではオーステナイト粒界に耐摩耗性お
よび耐損傷性に好ましくない初析フェライトが多量に生
成し、また０．８５％を超えるとオーステナイト粒界を
脆化させる有害な初析セメンタイトを生成させるばかり
か、レール頭部熱処理層や溶接部の微小偏析部にマルテ
ンサイトが生成し、靭性・延性を著しく損なうため０．
５５〜０．８５％に限定した。Next, the reason why the chemical composition of the deoxidized molten steel is limited as described above will be described. C is an essential element for strengthening and generating a pearlite structure,
Further, it is an element that uniquely exerts an effect on wear resistance as well, but if it is less than 0.55%, a large amount of proeutectoid ferrite which is unfavorable for wear resistance and damage resistance is generated in the austenite grain boundary, If it exceeds 85%, not only harmful harmful pro-eutectoid cementite that embrittles the austenite grain boundaries is generated, but also martensite is generated in the heat-separated layer of the rail head and the minute segregation part of the welded portion, which significantly impairs toughness and ductility. ．
It was limited to 55 to 0.85%.
【００１３】Ｓｉはパーライト組織中のフェライト層へ
の固溶体硬化による高強度化に寄与するばかりか、わず
かながらレール鋼の靭性・延性改善にも貢献する。ただ
し、０．２％以下ではその効果が期待できず、また、
１．２％を超えると脆化をもたらし溶接接合性も減ずる
ので、０．２０〜１．２０％に限定した。Si contributes not only to strengthening the ferrite layer in the pearlite structure by solid solution hardening, but also to slightly improving the toughness and ductility of the rail steel. However, if 0.2% or less, the effect cannot be expected, and
If it exceeds 1.2%, embrittlement is caused and weld bondability is also reduced, so the content is limited to 0.20 to 1.20%.
【００１４】ＭｎはＣ同様にパーライト変態温度を低下
させ、焼入性を高めることによって高強度化に寄与する
元素であるが、０．５％未満ではその効果が小さくまた
１．５０％を超えると偏析部にマルテンサイト組織を生
成させ易くするため０．５０〜１．５０％に限定した。Mn, like C, is an element that lowers the pearlite transformation temperature and contributes to strengthening by increasing the hardenability, but if it is less than 0.5%, its effect is small and exceeds 1.50%. In order to facilitate the formation of a martensite structure in the segregated portion, the content is limited to 0.50 to 1.50%.
【００１５】Ｓは一般に有害元素として知られている
が、本発明においてはオーステナイト粒内のマンガンシ
リケートなどの酸化物を核とするＭｎＳを基地とするＶ
炭化物が生成し、これを変態核とするパーライト組織が
生成するため欠かせない元素である。しかし、０．００
６％未満ではパーライト変態核としてのＭｎＳ量が減じ
てしまい、パーライト粒内変態を確保できなくする。ま
た０．０３５％以上ではＭｎＳが多量に生成し靭性・延
性を著しく低下させるため０．００６〜０．０３５％に
限定した。Although S is generally known as a harmful element, in the present invention, V based on MnS whose core is an oxide such as manganese silicate in austenite grains is used.
It is an indispensable element because carbide is generated and a pearlite structure that uses this as a transformation nucleus is generated. But 0.00
If it is less than 6%, the amount of MnS as pearlite transformation nuclei is reduced, and pearlite intragranular transformation cannot be secured. If it is 0.035% or more, a large amount of MnS is formed and the toughness and ductility are significantly reduced, so the content is limited to 0.006 to 0.035%.
【００１６】Ｃｒは、パーライト変態を低下させること
によって高強度化に寄与すると同時に、パーライト組織
中のセメンタイト層を強化することによっても耐摩耗性
向上に貢献するが、一方ではセメンタイトの衝撃靭性を
低下させる作用も有している。しかし、Ｃｒのセメンタ
イト強化作用は無視しがたく、さらに溶接継ぎ手部軟化
防止の観点からも微量のＣｒの添加も望ましい。そこで
強度確保に一定の寄与が期待されかつ靭性・延性を損な
わない範囲内で０．１〜１．０％に限定した。[0016] Cr contributes to higher strength by lowering the pearlite transformation and at the same time contributes to improving wear resistance by strengthening the cementite layer in the pearlite structure. On the other hand, it reduces the impact toughness of cementite. It also has the effect of causing it. However, the cementite strengthening effect of Cr cannot be ignored, and addition of a small amount of Cr is also desirable from the viewpoint of preventing softening of the welded joint. Therefore, it is limited to 0.1 to 1.0% within a range in which a certain contribution is expected to secure the strength and the toughness and ductility are not impaired.
【００１７】Ｖは本発明の重要な構成要素であるが、冷
却中にＭｎＳ上に析出させたＶ炭化物を核としたパーラ
イト変態の生成を見いだしたことにより、従来オーステ
ナイト粒界に限定されていたパーライト変態核がオース
テナイト粒内からも期待でき、結果として微細なパーラ
イト部からなるレール鋼を得ることができるようになり
大幅な靭性の向上を果たすことができた。しかし、０．
０１％未満では、この効果が弱く、また１．０％以上添
加するとＶ炭化物が粗大化し、レール頭部内部からの疲
労き裂発生起点となることから、Ｖ添加量を０．０１〜
１．０％の範囲に限定した。不可避的不純物元素である
Ｐは、レール鋼の靭性を向上させるためにはできるだけ
低減させることが望ましい。Although V is an important constituent of the present invention, it was conventionally limited to austenite grain boundaries by the fact that the formation of pearlite transformation centered on V carbides precipitated on MnS during cooling was found. The pearlite transformation nuclei can be expected even from within the austenite grains, and as a result, a rail steel composed of fine pearlite parts can be obtained, and the toughness can be greatly improved. However, 0.
If it is less than 01%, this effect is weak, and if it is added in an amount of 1.0% or more, V carbides are coarsened and become a starting point of fatigue crack initiation from inside the rail head.
It was limited to the range of 1.0%. It is desirable to reduce P, which is an unavoidable impurity element, as much as possible in order to improve the toughness of the rail steel.
【００１８】前記のような成分組成で構成されるレール
鋼は、転炉、電気炉などの通常使用される溶解炉で前述
した脱酸を含む溶製を行い、この溶鋼を造塊・分塊法あ
るいは連続鋳造法、さらに熱間圧延を経て製造する。熱
間圧延を終えたレールは、冷却中においてオーステナイ
ト粒内のＭｎＳに析出したＶ炭化物からもパーライト変
態が生成し、オーステナイト粒界から生成するパーライ
トとともに微細なパーライト粒を構成する。その結果、
圧延ままで靭性の優れた高強度レールを製造することが
できる。The rail steel having the above-described composition is subjected to smelting including the above-mentioned deoxidation in a commonly used smelting furnace such as a converter or an electric furnace, and this molten steel is agglomerated and agglomerated. Method or continuous casting method, and then hot rolling. The rails that have undergone hot rolling also undergo pearlite transformation from V carbides precipitated in MnS in austenite grains during cooling, and form fine pearlite grains together with pearlite produced from austenite grain boundaries. as a result,
A high-strength rail having excellent toughness can be manufactured as it is rolled.
【００１９】さらに高強度とともに高靭性が要求される
場合には、圧延終了後あるいは、一度室温に冷却され熱
処理する目的で再加熱されたオーステナイト域温度から
冷却する際に７００〜５００℃間を１〜５℃/secで加速
冷却されたレール鋼では、一層の高靭性が得られる。す
なわち、パーライト組織鋼の特徴として、加速冷却する
ことによって低温でパーライト変態を生じさせ、このこ
とによりパーライト変態核の生成速度が向上し結果的に
パーライト粒を微細にすることができるからである。従
ってＭｎＳ上に析出させたＶ炭化物からのパーライト組
織のオーステナイト粒内変態と、加速冷却によるオース
テナイト粒界からのパーライト変態が重畳して一層のレ
ール鋼の靭性向上を達成することができる。この際冷却
媒体は、空気あるいはミストなどの気液混合物を用い、
レール頭部もしくは底部の強度が１１００MPa 以上とす
ることが望ましい。When high strength and high toughness are required, a temperature between 700 and 500 ° C. is set after completion of rolling or when cooling from the austenite region temperature reheated once for the purpose of heat treatment after cooling to room temperature. Rail steels that have been accelerated cooled at ~ 5 ° C / sec can achieve even higher toughness. That is, as a characteristic of the pearlite structure steel, pearlite transformation is caused at a low temperature by accelerated cooling, whereby the generation rate of pearlite transformation nuclei is improved, and as a result, pearlite grains can be made fine. Therefore, the austenite intragranular transformation of the pearlite structure from the V carbides precipitated on MnS and the pearlite transformation from the austenite grain boundaries due to accelerated cooling can be superimposed to further improve the toughness of the rail steel. At this time, the cooling medium is a gas-liquid mixture such as air or mist,
It is desirable that the strength of the rail head or bottom be 1100 MPa or more.
【００２０】レール鋼の靭性評価法としては、ロシアの
ＧＯＳＴ規格によって定められた２mmＵノッチシャルピ
ー試験における＋２０℃での衝撃吸収エネルギーであ
り、同規格によれば高強度熱処理レールの＋２０℃での
衝撃吸収エネルギーは０．２５MJ/m2 以上が必要とされ
ている。上述したオーステナイト粒内のＭｎＳに析出さ
せたＶ炭化物をパーライト変態核として活用することに
よって、本発明のレール鋼ではパーライト粒が微細化
し、０．２５MJ/m2 以上の衝撃吸収エネルギーを得るこ
とができる。レールの延性はレール頭部の疲労損傷の生
成に影響を与え、中国における高強度レールの延性要求
は、レール頭部ＧＣ内部１０mm深さ位置から採取した平
行部径６mm、平行部長さ３０mmの引張試験において１２
％以上の伸び値が必要であるとしている。このような材
質要求に対して本発明のオーステナイト粒内に生成させ
たＭｎＳからパーライト変態を生成させることにより、
微細なパーライト組織を生成せしめ靭性同様にレール鋼
の延性も大幅に改善することができた。The toughness evaluation method of rail steel is the impact absorbed energy at + 20 ° C. in the 2 mm U-notch Charpy test defined by the GOST standard of Russia. According to the standard, the impact of high strength heat treated rail at + 20 ° C. Absorbed energy is required to be 0.25 MJ / m 2 or more. By utilizing the above-mentioned V carbides precipitated in MnS in the austenite grains as pearlite transformation nuclei, the pearlite grains are refined in the rail steel of the present invention, and impact absorption energy of 0.25 MJ / m 2 or more can be obtained. it can. The ductility of the rail affects the generation of fatigue damage to the rail head, and the ductility requirement of the high-strength rail in China is that the parallel section diameter of 6 mm and the parallel section length of 30 mm are taken from a depth of 10 mm inside the rail head GC. 12 in the test
It is said that an elongation value of at least% is required. In response to such material requirements, by generating a pearlite transformation from MnS generated in the austenite grains of the present invention,
The ductility of the rail steel as well as the toughness due to the formation of the fine pearlite structure could be greatly improved.
【００２１】[0021]
【実施例】次に本発明により製造した高靭性を有する高
強度レールの製造実施例について述べる。表１は供試鋼
の化学成分および用いた脱酸方法を示す。またＴｉ脱酸
を行った場合と脱酸制御を行わなかった場合、さらに脱
酸を行ったＶ無添加鋼のそれぞれ冷却後の組織中に認め
られる０．１〜１０μｍのＭｎＳ個数の測定結果を、ま
た冷却後の組織中にＭｎＳを核とするパーライト粒内変
態が含まれているかどうかを観察した結果を表２に示
す。Ｔｉ脱酸を行った本発明鋼および比較鋼では、所定
の量の微細なＭｎＳの生成が確認され、さらにＶ添加し
た本発明鋼では明らかにオーステナイト粒内からのＭｎ
Ｓを核としたＶ炭化物を生成起点としたパーライト組織
の生成が確認された。EXAMPLES Next, examples of production of high strength rails having high toughness produced according to the present invention will be described. Table 1 shows the chemical composition of the sample steel and the deoxidizing method used. In addition, when the Ti deoxidation was performed and when the deoxidation control was not performed, the measurement results of the MnS number of 0.1 to 10 μm observed in the structures of the V-added steels that were further deoxidized after cooling were obtained. Table 2 shows the results of observation as to whether or not the pearlite intragranular transformation having MnS as a nucleus is contained in the structure after cooling. It was confirmed that a predetermined amount of fine MnS was formed in the steels of the present invention and the comparative steels subjected to Ti deoxidation, and in the steels of the present invention in which V was added, the Mn from inside the austenite grains was clearly
It was confirmed that a pearlite structure was formed with a V carbide having S as a nucleus as a generation origin.
【００２２】表３には圧延まま、および強度を一定とす
るために化学成分毎にオーステナイト域温度から７００
〜５００℃間を冷却速度１〜５℃/secの範囲で変化させ
た加速冷却後のレール鋼の引張試験強度、伸びおよび２
mmＵノッチシャルピー試験における＋２０℃での衝撃吸
収エネルギー測定結果を示す。引張試験はレール頭部Ｇ
Ｃ内部１０mm深さ位置から採取した平行部径６mm、平行
部長さ３０mmの試験片で行った。この結果本発明鋼は、
比較鋼に比べて十分にパーライト微細組織の効果として
の延性の改善が認められた。衝撃試験片はレール頭部１
mm下より採取した。この試験条件は熱処理レールにおけ
る靭性を規定したロシアのＧＯＳＴ規格に基づくもの
で、同規格によれば高強度熱処理レールの＋２０℃での
衝撃吸収エネルギーは０．２５MJ/m2 以上が必要とされ
ており、本発明のＴｉ脱酸を行うことによってオーステ
ナイト粒内からもパーライト変態を生成させた微細パー
ライト組織鋼は、いずれもＧＯＳＴ規格に定められたシ
ャルピー吸収エネルギーを十分に満たしている。In Table 3, as-rolled and 700-700 from the austenite range temperature for each chemical component in order to keep the strength constant.
Tensile strength, elongation, and 2 of the rail steel after accelerated cooling in which the cooling rate was changed in the range of 1 to 5 ° C / sec.
The measurement result of the impact absorption energy in +20 degreeC in mmU notch Charpy test is shown. Tensile test for rail head G
A test piece having a parallel part diameter of 6 mm and a parallel part length of 30 mm was sampled from a depth position of 10 mm inside C. As a result, the steel of the present invention is
A sufficient improvement in ductility as an effect of the pearlite microstructure was observed as compared with the comparative steel. Impact test piece is rail head 1
It was collected from the bottom of mm. This test condition is based on the Russian GOST standard that regulates the toughness of heat-treated rails. According to this standard, high-strength heat-treated rails require impact absorption energy at + 20 ° C of 0.25 MJ / m 2 or more. Therefore, the fine pearlite structure steels in which the pearlite transformation is generated even in the austenite grains by carrying out the Ti deoxidation of the present invention all sufficiently satisfy the Charpy absorbed energy specified in the GOST standard.
【００２３】[0023]
【表１】 [Table 1]
【００２４】[0024]
【表２】 [Table 2]
【００２５】[0025]
【表３】 [Table 3]
【００２６】[0026]
【発明の効果】本発明のレール鋼の脱酸制御によってＭ
ｎＳの個数を制御することによりオーステナイト粒内の
ＭｎＳに析出させたＶ炭化物をパーライト変態核として
活用することにより、パーライト粒が微細化し、十分な
シャルピー衝撃値を得ることができ、レールの延性およ
び靭性も大幅に改善できる。EFFECT OF THE INVENTION By the deoxidation control of the rail steel of the present invention, M
By utilizing the V carbides precipitated in MnS in the austenite grains by controlling the number of nS as the pearlite transformation nuclei, the pearlite grains can be made fine and a sufficient Charpy impact value can be obtained, and the ductility of the rail and The toughness can also be improved significantly.
【図１】加速冷却有無における衝撃値に及ぼすＴｉ添加
の影響を示す図。FIG. 1 is a diagram showing the effect of Ti addition on the impact value with and without accelerated cooling.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 若生 昌光 千葉県富津市新富20−１ 新日本製鐵株式 会社技術開発本部内 (72)発明者 船木 秀一 千葉県富津市新富20−１ 新日本製鐵株式 会社技術開発本部内 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masamitsu Waka 20-1 Shintomi, Futtsu-shi, Chiba Shin Nippon Steel Co., Ltd.Technology Development Headquarters (72) Inventor Shuichi Funaki 20-1 Shintomi, Futtsu-shi, Chiba New Japan Iron & Steel Co., Ltd.
Claims (2)
て、重量％で Ｃ ：０．５５〜０．８５％、 Ｓｉ：０．２０〜１．２０％、 Ｍｎ：０．５０〜１．５０％、 Ｓ ：０．００６〜０．０３５％、 Ｃｒ：０．１〜１．０％、 Ｖ ：０．０１〜１．０％ を含有して残部が鉄および不可避的不純物からなり、
０．１〜１０μｍの大きさのＭｎＳが１mm2 あたり、３
０〜１００００個存在し、オーステナイト粒内のＭｎＳ
を核としたパーライトが存在することを特徴とする延性
および靭性に優れた高強度レール。1. A steel deoxidized by adding Ti, wherein C: 0.55 to 0.85% by weight, Si: 0.20 to 1.20%, Mn: 0.50. ˜1.50%, S: 0.006 to 0.035%, Cr: 0.1 to 1.0%, V: 0.01 to 1.0% with the balance being iron and unavoidable impurities Becomes
MnS having a size of 0.1 to 10 μm is 3 per 1 mm 2 .
There are 0 to 10000 MnS in austenite grains
A high-strength rail with excellent ductility and toughness, characterized by the presence of pearlite whose core is.
た、重量％で Ｃ ：０．５５〜０．８５％、 Ｓｉ：０．２０〜１．２０％、 Ｍｎ：０．５０〜１．５０％、 Ｓ ：０．００６〜０．０３５％、 Ｃｒ：０．１〜１．０％、 Ｖ ：０．０１〜１．０％ を含有して残部が鉄および不可避的不純物からなる溶鋼
から造塊・分塊法あるいは連続鋳造法を経て製造した鋼
片を、熱間圧延終了後、あるいは熱処理する目的で高温
に加熱した後、レールの頭部あるいはさらに底部を、オ
ーステナイト域温度から冷却する際に、７００〜５００
℃間を１〜５℃/secで加速冷却し、０．１〜１０μｍの
大きさのＭｎＳを１mm2 あたり３０〜１００００個生成
させ、オーステナイト粒内のＭｎＳを核としたパーライ
トを生成させることを特徴とする延性および靭性に優れ
た高強度レールの製造法。2. Deoxidation treatment by adding Ti and ingot production, C: 0.55 to 0.85% by weight, Si: 0.20 to 1.20%, Mn: 0.50 ˜1.50%, S: 0.006 to 0.035%, Cr: 0.1 to 1.0%, V: 0.01 to 1.0% with the balance being iron and unavoidable impurities After the hot rolling is finished, the steel slab produced from the molten steel by the ingot-agglomeration method or the continuous casting method is heated to a high temperature for the purpose of heat treatment. When cooling from 700 to 500
By accelerating cooling at a temperature of 1 to 5 ° C./sec, 30 to 10,000 MnS having a size of 0.1 to 10 μm is generated per mm 2 , and pearlite having MnS in austenite grains as a nucleus is generated. A method for manufacturing high-strength rails with excellent ductility and toughness.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7019493A JPH06279927A (en) | 1993-03-29 | 1993-03-29 | High strength rail excellent in ductility and toughness and its production |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7019493A JPH06279927A (en) | 1993-03-29 | 1993-03-29 | High strength rail excellent in ductility and toughness and its production |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH06279927A true JPH06279927A (en) | 1994-10-04 |
Family
ID=13424472
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7019493A Pending JPH06279927A (en) | 1993-03-29 | 1993-03-29 | High strength rail excellent in ductility and toughness and its production |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH06279927A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1997036016A1 (en) * | 1996-03-27 | 1997-10-02 | Nippon Steel Corporation | Low-alloy heat-treated pearlitic steel rails with excellent wear resistance and welding characteristics and process for production thereof |
| US20110253268A1 (en) * | 2010-04-16 | 2011-10-20 | Pangang Group Co., Ltd. | High carbon content and high strength heat-treated steel rail and method for producing the same |
| WO2013161548A1 (en) | 2012-04-27 | 2013-10-31 | 新日鐵住金株式会社 | Steel for vehicle wheel |
| EP2006406A4 (en) * | 2006-03-16 | 2015-08-12 | Jfe Steel Corp | High-strength pearlite rail with excellent delayed-fracture resistance |
| WO2021057094A1 (en) * | 2019-09-27 | 2021-04-01 | 武汉钢铁有限公司 | Production method that reduces residual stress of heat-treated steel rail and resulting steel rail |
| CN113699452A (en) * | 2021-08-30 | 2021-11-26 | 宝武集团马钢轨交材料科技有限公司 | Steel for tramcar elastic wheel rim and heat treatment method and production method thereof |
| CN114807779A (en) * | 2022-07-01 | 2022-07-29 | 北京科技大学 | Heavy rail steel and preparation process thereof |
-
1993
- 1993-03-29 JP JP7019493A patent/JPH06279927A/en active Pending
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1997036016A1 (en) * | 1996-03-27 | 1997-10-02 | Nippon Steel Corporation | Low-alloy heat-treated pearlitic steel rails with excellent wear resistance and welding characteristics and process for production thereof |
| AU690457B2 (en) * | 1996-03-27 | 1998-04-23 | Nippon Steel & Sumitomo Metal Corporation | Low-alloy heat-treated pearlitic steel rails |
| EP2006406A4 (en) * | 2006-03-16 | 2015-08-12 | Jfe Steel Corp | High-strength pearlite rail with excellent delayed-fracture resistance |
| US20110253268A1 (en) * | 2010-04-16 | 2011-10-20 | Pangang Group Co., Ltd. | High carbon content and high strength heat-treated steel rail and method for producing the same |
| US9157131B2 (en) * | 2010-04-16 | 2015-10-13 | Pangang Group Co., Ltd. | High carbon content and high strength heat-treated steel rail and method for producing the same |
| WO2013161548A1 (en) | 2012-04-27 | 2013-10-31 | 新日鐵住金株式会社 | Steel for vehicle wheel |
| CN104254631A (en) * | 2012-04-27 | 2014-12-31 | 新日铁住金株式会社 | Steel for vehicle wheel |
| EP2843071A4 (en) * | 2012-04-27 | 2016-04-20 | Nippon Steel & Sumitomo Metal Corp | Steel for vehicle wheel |
| US9850560B2 (en) | 2012-04-27 | 2017-12-26 | Nippon Steel & Sumitomo Metal Corporation | Steel for wheel |
| WO2021057094A1 (en) * | 2019-09-27 | 2021-04-01 | 武汉钢铁有限公司 | Production method that reduces residual stress of heat-treated steel rail and resulting steel rail |
| CN113699452A (en) * | 2021-08-30 | 2021-11-26 | 宝武集团马钢轨交材料科技有限公司 | Steel for tramcar elastic wheel rim and heat treatment method and production method thereof |
| CN114807779A (en) * | 2022-07-01 | 2022-07-29 | 北京科技大学 | Heavy rail steel and preparation process thereof |
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